Lighting device



March 29,'1932. F. ALEXANDER LIGHTING DEVICE Filed May 31. 1927 vwemoz FOCSanea/n/ Alexander Patented Mar. 29, 1932 .UNITED STATES .PATENT oFFIcEj-v- EoCsANEANU ALEXANDER, OE NEW YORK, N. Y., AssIGNOR ToARGco TUBE AND TELE- vIsION CORPORATION, A CORPORATION OE DELAWARE LIGHTING DEVICE Application led May 31, 1927. Serial No. 195,889.

vThe present invention relates to lighting devices of the type that comprises a glass tube or bulb containing an-atmosphere of a condulztive gas and electrodes enclosed within the tu e.

Such tubes frequently contain one or more of the noble gases, such as neon, argonor helium, or mercury vapor, the gas being at relatively light pressures. When current is passed, the gas becomes ionized and there is a` yso depleted by combination with the evaporated material that in 'a comparatively short time the tube ceases to function.

In order to obviate this 'condition it--has heretofore been the practice to form the electrodes in such manner that they might have a large superficial area. Careful experiment has resulted in the finding that the smallest superficial area that will give practical results in eiciency and life is 1.5 square decil meters per ampere. AAs the area of the surface increases above this ligure, the heating edect due to the current is less and the evaporation correspondingly smaller.

Luminescent tubes having a relatively long life may indeed be made in this manner, for

y'the very large'superficial areas of the electrodes permit a cooling effectA due to the amount of heat which is radiated from such large surfaces. However, as the radiated heat is confined Within the narrow space of the electrode chamber, after a relatively short period of operation this advantage is lost and the confined heat of radiation serves once more to elevate the temperature of the electrodes-and evaporation and depletion of the gas proceeds. In' addition to this, electrodes ofsuch large size are unsightl in appearance and present practical diiicultles in themanufacture of the tubes.

It is an object of .the presentfirivention to provide a luminescent tube whiclifwill oper life and which will avoid fthe-defects above" mentioned. It is a. further objecttoprovide an electrode .for such tubes having-a su'pricial area substantially less thanlf. t decimeters per ampere. It is affst object to provide means for coolin' `suchelectrodes by carrying away the heatffrom the Jsame and radiating it outside the electrode chamber and outside thev tube. v f -I Other objects and advantages will appear lfrom a consideration of the forms of the de`r vice illustrated in the drawings to which reference is now made. l Fig. 1 is a view in elcvationof a luminescent tube embodying the invention.

Fig. 2 is a longitudinal section through one, end of said tube. v f Fig. 3 is a view in perspective of Ithe electrode and heat radiating structure of `said tube.

Referrin` which mayie of any suitable form or dimenf sions. Into the ends of the tube, 1, 'are'sealed the electrodes, 3. At thc'oute'r'fend 'ofthegheat -ate with great efficiency during a long useful to Fig.` 41, 1 indicates the .tube l' I' -the heat dissipating elements, 2, which' carryi-4 l t dissipating element 2, which consists, preferably, of a `cylinder of copper 'ofrelativel large size with respect to the.electrode',f

Connection is made with asource ofelectric` current not shown by the conductors, 4,5 The electrode, 3, maybe of iron, aluminium', 'copper or other suitable metal. 'It may be' of any suitable size above or below 1.5 squarefdeci`v meters perv ampere and is mounted in a-cup; 5,1

formed by the'hollowed outinnerfendof the il heat dissipating element, 2.5 The rini,.6,of 90.

the cup, 5, is madev very, thin to facilitate the formation of a seal with the glass ofthe tube,

1, in the manner hereinafter described.

The electrodes, 3, if vformed of a metal different from that of the heat-dissipating element, v2,'isx set into afhole'-,-",` as indicated'v in Fig. 2, and may be iNedtherefSby a vs r'eliling. soldering, riveting, or, byiathread, or' otherwise. A suiicient area of the surface ofthe electrodeis thus in intimate contact with the heat dissipating element,tov impart its heat tion of the element .which is external to the tube. If on the other hand the heat dissipating element and the electrode are. of the same metal, they.. may be turned out of single' piece and embodied in one structure. .It will be evident that the heat dissipating element, 2,- .performs the function of leading current to the electrode, 3, inaddition to that of carrying the heat away therefrom and radiating it outside the tube. For this rea-4 son, I prefer to form the heat dissipating element of a metal of superior electrical and thermal conductivity such as copper. Furth'ern'ior'e I'may protect this element, 2, by a casing `o1"gu:`1rd,' made of a material which is a poor conductor of electricity,fas for exam-ple'glass or hard rubber, provided with v`"perforations to facilitate the escape of the he'at'of radiation. This is desirable in some cases to avoid accidental shocks but not on account of the heat ofthe element, for even during long operation the heat dissipating element remains sufliciently cool to enable one to touch it without being burned.

InFig. l3, the heat dissipating element is shown in perspective so as to display the cup into'which they electrode is set. The element is 'turned out of a single piece, preferably of copper for the reasons above set foiith, `and one' end is hollowed out to form a depression, 5, with a rim, 6, of very great thinness, of the orderof .005 to .Ol0`inch. In the center of the floor, 5, of this depression or cup, is the ends of said tube, theelectrode constructionrf comprising a. heat-radiating metallic body external to the tube adjacent an end thereof with its face closing the mouth of the tube, said metallic body at said face being formed l with a thin walled annular Harige surr unding and sealed to the wall voit' the jtube;

and said metallic body further being prov vided at said face with a nctallic projection ally into the tube; and a cap of electrically non-conductive material enclosing said metallic body, said cap being interiorly larger vforming the actualelectrode projecting aXithan said body so` as to be air-spaced there- Y from and being perforated for circulation of 'atmospheric air to and from the metallic body. v

In witness whereof, I have hereunto subscribed my name this 19th day of May, 1927.

FOCSANEANU ALEXANDER.

hole,f7, bored tol'accom'modate the electrode, y

a, of Figfa.

After the electrode, 3,*has been mounted in I the hole, 7, the heat dissipating element, 2, is sealed to the glass tube, 1.,' in the following manner. It is well known that'fused lass the copper will dra'waway from the glass because of the difference in coeiicient of expansion. If, however, the edge of the vcopper be made of the order of thinness above mentioned, from .Q05 to .010 inch, when the end of the glass tubeis softened by heat and the thin rim, 6, also heated is pushed into it and held therel until cooling, a good airtight. seal is made'.

l/Vhe'n the seals are formed in this manner is remarkable for its brilliancy and the mainwill easily welt copper, but that on coo ing Y 

